1. Field of the Invention
The invention relates generally to digital pattern recognition systems and, more particularly, but not by way of limitation, it relates to an improved form of pattern detection device for use with multidimensional data in the presence of noise.
2. Description of the Prior Art
Generally, the prior art has been limited to various forms of two-dimensional recognition process wherein digital image processing is carried out using flat or two-dimensional operators in processing a single image plane and the selection of thresholds is a difficult task at best. The prior art proposals employed a variety of operators for detection of edges and lines by fitting a surface to a picture function in the neighborhood of each image point and then taking the derivatives of the function at that point. The prior operators worked on single plane images and thereby required a very difficult and time consuming threshold selection procedure. Such prior art digital picture processing technique is disclosed by Prewitt in "Object Enhancement and Extraction in Picture Processing and Psycho Pictorics", Academic Press, New York, 1970, pp. 75, 149. More recently, Haralick introduced the noise term and devised statistical tests for the detection of significant edges by fitting a plane in the neighborhood of a point for a two-dimensional image, and this teaching is presented in "Edge and Region Analysis of Digital Image Data" as presented in Computer Graphics and Image Processing, Volume 12, 1980, PP. 60-73.
Several prior sources have treated the surface fitting using an orthogonal basis of two-dimensional functions, i.e. walsh functions, orthonormal fourier functions and orthogonal polynomials, and here again all of the operators work upon a two-dimensional plane or single band image. Still more recently, Morgenthaler and Rosenfeld generalized the aforementioned Prewitt operators to n-dimensions by fitting a hyperquadric surface. However, noise is not introduced into the formulation. The Morgenthaler and Rosenfeld teachings are presented in an article entitled "Multidimensional Edge Detection by Hypersurface Fitting", IEEE Transactions, Pattern Analysis and Machine Intelligence, July 1981, PP. 482-486.
In the patented prior art, some patents of general interest are as follows: Sternberg--U.S. Pat. No. 4,322,716; Golay--U.S. Pat. No. 4,060,713; and Kono--U.S. Pat. No. 4,110,736.